Show soundtrack covers and edit alternative names (#49)

Covers: statistics cards show the soundtrack's cover on the left, and the
statistics popup shows it large. Until it arrives, and without a cover, the
soundtrack's initials stand in. Covers load only for cards on or near the
screen, three at a time, and are cached in covers/ next to the settings
(CoverCache), downloaded again only when cover_modified changes. The index and
file handling are shared with CharacterCache in a new FileCache.

Alternative names: the popup shows them and has an editor (add, remove, save)
that sends PUT /soundtracks/{uuid}/alternative-names. The statistics search and
the Search popup find soundtracks by them; Search shows the matching name after
the real one. Search now loads /soundtracks, falling back to the plain list.

The API types are regenerated from the server's spec, with a SoundtrackCover
theme style in every theme.

Closes #49

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/music_server_client.gd

@@ -131,6 +131,31 @@ func fetch_soundtracks(on_done: Callable, on_failed: Callable = Callable()) -> v
 	get_json_list("/soundtracks", Soundtrack, on_done, on_failed)
 
 
+## Downloads the cover picture of the soundtrack with [param uuid] as bytes (JPEG or
+## PNG). The server answers 404 while it has no cover for it.
+func fetch_soundtrack_cover(
+		uuid: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
+	get_bytes("/soundtracks/%s/cover" % uuid.uri_encode(), on_done, on_failed)
+
+
+## Replaces the alternative names of the soundtrack with [param uuid] with
+## [param names]. The server trims them, drops duplicates and the soundtrack's own name,
+## and calls [param on_done] with the updated [Soundtrack].
+func set_alternative_names(uuid: String, names: Array[String], on_done: Callable,
+		on_failed: Callable = Callable()) -> void:
+	var request: AlternativeNames = AlternativeNames.new()
+	request.names = names
+	var path: String = "/soundtracks/%s/alternative-names" % uuid.uri_encode()
+	var saved: Callable = func saved(data: Variant) -> void:
+		if !(data is Dictionary):
+			push_warning("Expected a JSON object from " + path)
+			_call_if_valid(on_failed)
+			return
+		on_done.call(Soundtrack.from_dict(data))
+	_request(path, HTTPClient.METHOD_PUT, _parse_json.bind(path, saved, on_failed), on_failed,
+			true, JSON.stringify(request.to_dict()))
+
+
 ## Fetches a soundtrack and its songs as a [SoundtrackWithSongList].
 func fetch_soundtrack(
 		uuid: String, on_done: Callable, on_failed: Callable = Callable()) -> void:
@@ -419,13 +444,14 @@ func _parse_json(
 
 
 # Sends the request with the token, and once more with a new token if the server
-# answers 401
+# answers 401. A [param json_body] is sent as the request's body.
 func _request(
 		path: String,
 		method: int,
 		on_success: Callable,
 		on_failed: Callable,
 		may_retry: bool = true,
+		json_body: String = "",
 ) -> void:
 	_with_token(func(token: String) -> void:
 		_send(path, method, token, func(response_code: int, body: PackedByteArray) -> void:
@@ -433,10 +459,10 @@ func _request(
 				GameLog.debug("Token refused by the server, getting a new one")
 				if _token == token:
 					clear_token()
-				_request(path, method, on_success, on_failed, false)
+				_request(path, method, on_success, on_failed, false, json_body)
 				return
 			_handle_response(path, response_code, body, on_success, on_failed)
-		)
+		, json_body)
 	, on_failed)